System and method for broadband millimeter wave data communication

ABSTRACT

A system and method for information communication between physically separated processor-based systems. Disclosed is a centralized communication array providing point to multipoint information communication between processor-based systems utilizing communication nodes. Such information communication may be between two processor-based systems, each utilizing communication nodes or may be between a processor-based system utilizing a communication node and a processor-based system coupled to the centralized communication array through a backbone.

RELATED APPLICATIONS

The present application is a divisional of co-pending commonly assignedU.S. patent application Ser. No. 08/740,332 entitled “System and Methodfor Broadband Millimeter Wave Data Communication,” filed Nov. 7, 1996,the disclosure of which is incorporated herein by reference.

The present application is being concurrently filed with commonlyassigned U.S. patent application Ser. No. 09/434,832 entitled “SYSTEMAND METHOD FOR BROADBAND MILLIMETER WAVE DATA COMMUNICATION” andconcurrently filed with commonly assigned U.S. patent application Ser.No. 09/434,815 entitled “SYSTEM AND METHOD FOR BROADBAND MILLIMETER WAVEDATA COMMUNICATION” and concurrently filed with commonly assigned U.S.patent application, Ser. No. 09/434,816 entitled “SYSTEM AND METHOD FORBROADBAND MILLIMETER WAVE DATA COMMUNICATION”, the disclosures of whichare incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

This invention relates to broadband radio frequency communicationsystems and methods and more particularly to a system and method whichprovides for broadband information communication between processor-basedsystems through a centralized communication array.

BACKGROUND OF THE INVENTION

In the past, information communication between processor-based systems,such as local area networks (LAN) and other general purpose computers,separated by significant physical distances has been an obstacle tointegration of such systems. The choices available to bridge thephysical gap between such systems have not only been limited, but haverequired undesirable tradeoffs in cost, performance, and reliability.

One group of historically available communication choices includes suchsolutions as the utilization of a standard public switch telephonenetwork (PSTN) or multiplexing signals over an existing physical link tobridge the gap and provide information communication between thesystems. Although such solutions are typically inexpensive to implement,they include numerous undesirable traits. Specifically, since theseexisting links are typically not designed for high speed datacommunication, they lack the bandwidth through which to communicatelarge amounts of data rapidly. As in-building LAN speeds increase to 100Mbps, the local PSTN voice grade circuits even more markedly represent achoke point for broadband metropolitan area access and therefore arebecoming a less and less desirable alternative. Furthermore, suchconnections lack the fault tolerance or reliability found in systemsdesigned for reliable transmission of important processor-based systeminformation.

Another historically available group of communication choices is foundat the opposite end of the price spectrum than those mentioned above.This group includes such solutions as the utilization of a fibre opticring or point to point microwave communication. These solutions aretypically cost prohibitive for all but the larger users. The point topoint systems require a dedicated system at each end of thecommunication link which lacks the ability to spread the cost of suchsystems over a plurality of users. Even if these systems were modifiableto be point-to-multipoint, to realize the economy of multiple system useof some system elements, the present point-to-point microwave systemswould not provide broadband data services but rather traditional bearerservices such as T1 and DS3. Furthermore these systems typically providea proprietary interface and therefore do not lend themselves to simpleinterfacing with a variety of general purpose processor-based systems.

Although a fibre optic ring provides economy if utilized by a pluralityof systems, it must be physically coupled to such systems. As the costof purchasing, placing, and maintaining such a ring is great, even theeconomy of multi-system utilization generally does not overcome theprohibitive cost of implementation.

A need therefore exists in the art of information communication for acommunication system providing cost effective bridging of large physicaldistances between processor-based systems.

A further need exists in the art for a communication system providinghigh speed broadband information communication between processor-basedsystems.

A still further need exists in the art for a fault tolerantcommunication system providing reliable bridging of physical gapsbetween processor-based systems.

Additionally, a need exists in the art for a broadband communicationsystem providing simple connectivity to a variety of processor-basedsystems and communication protocols, including general purpose computersystems and their standard communication protocols.

SUMMARY OF THE INVENTION

These and other objects, needs and desires are obtained in a system andmethod of communication in which a communication array, or hub, iscentrally located to provide an air link between physically separatedprocessor-based systems, or other sources of communication such as voicecommunication, utilizing a communication device, or node, of the presentinvention. Preferably, this central array may be physically coupled toan information communication backbone providing communication betweenair linked systems and physically linked systems. Furthermore, multipleones of such system may be utilized to bridge large physical separationof systems by the intercommunication of multiple central arrays.Moreover, pervasive surface coverage may be provided by arranging aplurality of such communication arrays to provide a cellular likeoverlay pattern.

In a preferred embodiment, the central communication array comprises aplurality of individual antenna elements in time division multiplex(TDM) communication with a processor-based system. This system processessignals received at each antenna element in order to route them to theirdesired destination. An advantage of using a plurality of individualantenna elements at the central communication array is that only antennaelements having a radiation pattern overlaying a remote site requiringcommunication service (subscriber) need be implemented at any particulartime. Thereafter, as more subscribers require service by a particularhub, additional antenna elements may be installed. This modularexpansion of the service capabilities of a hub results in reducedinitial installation costs where only a few subscribers initiallyrequire service, while maintaining the flexibility for implementation ofomni directional and/or cellular overlay communication coverage notpossible with point-to-point systems.

Also in a preferred embodiment, the communication spectrum utilized bythe communication system is frequency division multiplexed (FDM) toprovide multiple channels for simultaneous information communication toa plurality of subscribers. In addition to simultaneous informationcommunication to the subscribers, FDM channels may also be used tocommunicate control information through a predetermined band to networkelements simultaneously with the transmission of other data.

Preferably a carrier frequency in the millimeter wavelength spectrum,such as 10 to 60 GHz, is used by the present invention. Such carrierfrequencies are desirable in order to provide a communication bandwidthsufficient for the transmission of at least 30 Mbps through each definedFDM channel of approximately 10 MHZ.

The FDM channels may provide full duplex by defining a transmit (Tx) andreceive (Rx) channel pair as a single frequency division duplex (FDD)channel to serve a subscriber. However, it shall be appreciated that theprovision of full duplex by FDD is at the expense of depletion of theavailable spectrum at an increased rate as service to a singlesubscriber actually requires two channels.

In addition to multiplexing communication on frequency divided channels,time division multiplexing may be utilized to provide multiple,seemingly simultaneous, communications on a single FDM channel. Hereones of the FDM channels are broken down into a predetermined number ofdiscrete time slices (burst periods) which form a frame. Each burstperiod may be utilized by a different subscriber so as to result ininformation communication contained in a single frame, having a numberof TDM bursts, being directed to/from a number of subscribers over asingle FDM channel.

Moreover, full duplexing may be synthesized on a single FDM channel bytime division duplexing (TDD) through the use of burst periods likethose used in TDM. Through TDD, Tx and Rx frames, each frame having oneor more burst periods, are defined to provide communication in aparticular direction at a predefined time.

It shall be appreciated any of the aforementioned FDM, FDD, TDM, and TDDschemes, or their like, may be utilized in any combination deemedadvantageous. For example, a single frequency division channel may betime division multiplexed to provide communication to a number ofsubscribers while simultaneously being time division duplexed tosynthesize full duplexed communication with these subscribers.

In the above described embodiments, the communication system may utilizean initialization algorithm, perhaps including a token passingarrangement for shared data users, to poll subscriber's systems anddetermine communication attributes of each such system at each antennaelement of the central array. This information may be utilized todetermine the optimum assignment of resources, including antennaelements, TDM burst periods, FDD frequency assignments, and TDD Tx andRx time assignments for each such system. This information mayadditionally be utilized to provide secondary assignment of resources tomaintain system integrity in the event of an anomalous occurrence,thereby providing system fault tolerance.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter, which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand the specific embodiment disclosed may be readily utilized as a basisfor modifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates the interconnection of processor-based systems of apreferred embodiment of the present invention;

FIG. 2A illustrates an isometric view of the centralized communicationarray of a preferred embodiment of the present invention;

FIG. 2B illustrates a horizontal plane cross section view of thecentralized communication array depicted in FIG. 2A;

FIG. 2C illustrates a vertical plane cross section view of thecentralized communication array depicted in FIG. 2A;

FIG. 3A illustrates an embodiment of the composition of a signalcommunicated by the present invention during a time division multipleaccess burst period;

FIG. 3B illustrates an embodiment of the composition of a signalcommunicated by the present invention during a time division duplexburst period;

FIG. 4 illustrates an embodiment of a node of the present invention;

FIG. 5 illustrates an embodiment of the initialization algorithmutilized in configuring communication between the centralizedcommunication array and nodes of the present invention;

FIG. 6 illustrates the interconnection of processor-based systemsthrough a network of hubs of the present invention; and

FIGS. 7-8 illustrates of a preferred embodiment of the variouscomponents of a hub of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides high speed data communication via abroadband air interface allowing data access between subscriber'sremotely located systems. Referring to FIG. 1, it can be seen that suchwireless communication may be utilized, for example, to provide highspeed bridging of a physical gap between a plurality of processor-basedsystems, as illustrated by system 100. The processor-based systems mayinclude local area networks (LAN), such as LANs 110 and 120, orindividual computer systems, such as PC 130. It shall be appreciatedthat the processor-based systems utilizing the present invention may begeneral purpose computers, both standing alone and interconnected suchas by a LAN. Furthermore, the system can connect other communicationsystems such as voice or video in combination with, or in place of,communication sourced by the above mentioned processor-based systems.

Systems bridged by the present invention may utilize a communicationdevice, hereinafter referred to as a “node,” for communicating with acentralized communication device also of the present invention,hereinafter referred to as a “hub.” Still referring to FIG. 1, a hub isillustrated as element 101 and several nodes are illustrated as elements150, 151, and 152 connected to LANs 110 and 120 as well as to PC 130.

Also, as illustrated in FIG. 1, such wireless communication may beutilized to provide high speed communication between a processor-basedsystem, having a node coupled thereto, and communication backbone, suchas backbone 160, through hub 101. It shall be understood that backbone160 may be any form of communication means, such as a broadbandfibre-optic gateway or other broadband data grade connection, TIcommunications lines, a cable communication system, the Internet, or thelike, physically connected to hub 101. Moreover, backbones, such asillustrated by backbone 160, may be utilized to interconnect a pluralityof hubs into a communications network.

A communication network comprising a plurality of hubs is illustrated inFIG. 6. Through such a network, a node, such as node 150, in directcommunication with one hub, such as hub 101, may communicate with anode, such as node 621, in direct communication with another hub, suchas hub 620. Such communication may be accomplished through the two hubsinterconnection via a backbone, such as backbone 160. Of course, itshall be understood that intercommunication between hubs may beaccomplished through information “back-hauling” via air gapcommunication between two hubs such as is illustrated with hubs 101 and630. It shall be appreciated that a communications network may includeany number of hubs in communication with other hubs, through such meansas air gap or direct backbone interconnection, or the like. Informationcommunicated from a node in direct communication with one hub may berouted through various such interconnections to a node in directcommunication with any hub of the communication network.

In a preferred embodiment, the hub of the present invention is an omnidirectional antenna array having a plurality of individual antennaelements. One such individual antenna element is depicted as antennaelement 200 in FIG. 2A. The antenna elements are narrow beam directionalantennas having a predetermined communication lobe. These antennaelements are arranged in an array to provide an omni directionalcomposite radiation pattern. However it shall be understood that onlythe number of antenna elements required to communicate with apre-determined number of remote systems, rather than an omni directionalconfiguration, may be used, if desired.

Preferably, the antenna elements comprising hub 101, such as antennaelement 200, provide directional reception of extremely high frequency(EHF), such as that of 38 GHz providing millimeter wave (mmWave)communication in the Q-band. Such frequencies are advantageous as theyhave small wave lengths which are desirable for communication by highlydirectional antennas. Moreover, antennas utilized for communication ofsuch frequencies may be physically small while providing large signalgain.

The combination of such highly directional antennas with high gainprovides for improved frequency reuse and reduces the likelihood ofmulti-path interference. Additionally, the large gain realized by suchantennas is necessary to allow for communication over a reasonabledistance from the antenna, such as, for example, three (3) miles frompoint to point while using reasonable power levels.

Furthermore, such frequencies have only recently been licensed by theUnited States Government for use in radio communications. As such, thisfrequency range is not currently in pervasive use by othercommunications technologies. However, it shall be understood that theadvantages of the present invention may be realized by the use of anyfrequency band providing ability to communicate data at high speeds,providing that the selected band yields at least one channel ofapproximately 10 MHZ.

In the preferred embodiment, where omni-directional coverage by hub 101is to be utilized, individual antenna elements are arranged azimuthally,as illustrated in FIG. 2B, to cover a full 360 degree radius in ahorizontal plane. It shall be appreciated that arranging antennaelements in this manner can provide blanket radio communication coverageradially about hub 101 by selecting the communication lobe of eachantenna element to provide coverage in areas where the neighboringantenna elements are not so providing coverage.

Of course, as discussed above, the addition of antenna elementssufficient in number to provide a full 360 degree radiation pattern maybe accomplished modularly as system use demands. It shall be appreciatedthat, even where ultimately 360 degree coverage is desired, the modularnature of the individual antenna elements provides an economic means bywhich to provide initially limited coverage to a developing area. Forexample, where only a few locations, or subscribers, within a geographicarea covered by a particular hub site are desirous of communications bythe present invention, a hub, including only those antenna elementsnecessary to service these subscribers, may be erected. Thereafter, asadditional subscribers desire service within the service area of thehub, additional antenna elements may be added to the hub to provideservice to their associated nodes. Ultimately the hub may be filled outwith individual antenna elements to achieve communications in a full 360degree radius about the hub.

Provision of a hub of the present invention which may be expanded toinclude additional antenna elements may be accomplished in a number ofways. For example, a hub frame adapted to accept individual antennaelements at predetermined positions may be initially erected.Thereafter, individual antenna elements may be coupled to this hub framein positions corresponding to areas requiring service or increasedservice density.

Similarly, a hub mast and platter, or other support structure, may beinitially erected. As areas serviced by the hub require service orincreased service density, individual antenna element structures couldbe added to the hub support structure. In this embodiment, each antennaelement includes its own support and mounting structure to couple it tothe hub support structure and any neighboring antenna elementstructures. It shall be appreciated that such an embodiment provides forreduced startup cost where only a few antenna elements are required toinitially service the area. Furthermore, such an embodiment provides formore flexibility in positioning individual antenna elements as theantenna elements are not limited to positioning dictated by apreexisting frame structure.

Preferably, a total of 22 individual antenna elements, having acommunication lobe with approximately a 16 degree azimuthal beam widthand a 2.5 degree elevational beam height, are utilized to accomplish 360degree communication about hub 101. However, any number of individualelements could be utilized depending on individual design constraints,such as the presence of reflected waves and their associated multipathinterference. Additionally, as discussed above, only the number ofantenna elements needed for communication with certain identified nodes150 may be used if desired.

Experimentation has revealed that the use of antenna elements with a 16degree azimuthal beam width is advantageous in providing a desirablereuse of channels, both at the hub and in a cellular overlay patternproviding channel reuse of the various hubs. For example, an antennaelement operating in the mm Wave spectrum, configured as described aboveto have approximately a 16 degree beam, has been found to have side lobecharacteristics to permit reuse of the same channel at an antennaelement located on the same hub displaced approximately 90 degreesradially.

Still referring to FIG. 2B, it can be seen that each antenna element 200of the preferred embodiment is comprised of horn 210 and module 220. Inthe preferred embodiment, where EHF is used, horn 210 is a hybrid modelens corrected horn providing approximately 32 dB of gain. Module 220 isa synthesized mm Wave front-end module accepting and transmitting 38 GHzradio frequency energy through horn 210 converted to/from anintermediate frequency (IF), such as in the range of 400-500 MHZ, forcommunication with a modem, such as modem 240 illustrated in FIG. 2C. Ofcourse, depending on the carrier frequency used, the components of theantenna elements may be different than that stated above. Likewise, thehorn and module attributes of the antenna elements may be different thanthat stated above where, for example, a different carrier frequency orbeam pattern is desired.

Preferably, modem 240 is a wideband modem capable of 42 Mbps throughputusing quadrature amplitude modulation (QAM). As will be discussedhereinafter, the system may utilize a variable rate modem, such as isavailable commercially from various manufacturers including BroadComCorporation, Philips, and VLSI Technology. Such a variable rate modemprovides for the transmission of variable information densities (i.e.,various numbers of bits per symbol), for example from 17 to 51 Mbps(corresponding to 4 QAM, encoding two bits per symbol, up to 256 QAM,encoding 8 bits per symbol), at a fixed baud rate, such as 8.5 Mbaud.Typically such a modem utilizes matched data filtering that results inan occupied RF bandwidth that is 15% to 30% in excess of the theoreticalNyquist bandwidth. The variable modem can be useful in increasingspectral efficiency by changing the density of the informationcommunicated to the served users depending on communication attributessuch as their relative distance from the hub.

For example, an increased density of data in a particular time frame maybe communicated to a node, geographically positioned near a hub, by theuse of 256 QAM using the same occupied RF bandwidth and substantiallythe same transmitter power as the transmission of a signal containing adecreased density of data to a node, geographically positioned on thefringe of the hub's radiation pattern, by the use of 4 QAM. Thetransmission of increased data density to the near node without the needfor significantly increased power is achievable in part because oflessened effects of signal attenuation, and thus a higher signal tonoise ratio associated with a given power level, for the near node ascompared to the far node. The higher signal to noise ratio experiencedat the near node can typically sustain increased information density.However, regardless of the transmission density ultimately settled upon,when using a variable rate modem it may be advantageous to initiallysynchronize the system using lower order modulation and subsequentlyswitch to higher order modulation for a given node.

Link management information, such as control signals adjusting theaforementioned information density, and/or error correction informationmay be multiplexed as control information into the data streamcommunicated by the modem. For example, the control information mayinclude multiplexed filtering and error correction information, such asforward error correction (FEC) data embedded in the data stream. Ofcourse, any number of methods of providing link management and errordetection/correction may be provided through the use of informationmultiplexed through a data stream communicated by a modem of the presentinvention.

In a preferred embodiment, the individual antenna elements are arrangedin a number of tiers. These tiers may simply be an identified group ofantenna elements, or may be a physically delineated arrangement ofantenna elements. Regardless of their physical interrelationship, a tierof antenna elements includes any number of antenna elements havingsubstantially non-overlapping radiation patterns. Illustrated in FIG. 2Cis one embodiment including three vertical tiers of antenna elements.Each tier of hub 101 is preferably disposed to provide substantially thesame far field radiation pattern. However, antenna elements of differenttiers are preferably adapted to provide simultaneous communication on achannel, or channels, different than antenna elements having overlappingradiation patterns. For example an antenna element from a first tier maycommunicate through the use of a first frequency band while an antennaelement from a second tier communicates through the use of a secondfrequency band. Similarly, the antenna element from the first tier may,although utilizing a same set of channels as an antenna element of thesecond tier, communicate through one particular channel of the set whilethe antenna element of the second tier communicates through a differentchannel. The use of these different frequencies provides a convenientmeans by which additional communication capacity may be served in adefined geographic area.

Of course, the hub is fully scalable and may include a number of tiers,different than that illustrated. Any number of tiers, including anynumber of antenna elements, may be utilized by the present invention.For example, a single tier of antenna elements may be used to provideomni directional communication from hub 101 where increasedcommunication density is not required. Similarly, two tiers, eachincluding only a single antenna element, may be used to provideincreased capacity in a limited area defined by the radiation pattern ofthe antenna elements.

Moreover, subsequent addition of tiers to the hub may be accomplished,as was discussed above with respect to the addition to individualantenna elements. For example, where it is determined that a hubincluding any combination of tiers is insufficient to provide therequired communication density, antenna elements comprising any numberof additional tiers may be added. Of course, where only a particularportion of the area serviced by the hub requires increased communicationdensity, the added tiers may include only those antenna elements havinga radiation pattern covering the particular portion needing increasedcommunication density, if desired.

Alternatively, the tiers of antenna elements could be disposed toprovide different radio communication coverage areas about hub 101. Suchdifferences in radio communication coverage may be accomplished, forexample, by adjusting the different tiers to have differing amounts of“down tilt” with respect to the vertical axis. Down tilt of the tiersmay be accomplished by the physical tilting of the individual antennaelements or by any number of beam steering techniques known in the art.Additionally, adjustment of the down tilt may be made periodically, suchas dynamically during antenna operation, by the inclusion of amechanical adjustment or the aforementioned beam steering techniques.

Additionally, antenna elements having different radiation patternattributes may be utilized to provide the defined radio communicationcoverage areas discussed above. For example, antenna elements utilizedto provide communication in an area near a hub may provide a radiationpattern having a broader beam, and thus a lower gain, than the preferredembodiment of the antenna elements described above. Likewise, antennaelements utilized to provide communication in an area more distant fromthe hub may provide a radiation pattern having a narrower beam, and thusa higher gain.

Where the antenna elements of a tier have a different down tilt orradiation pattern, the individual tiers could be used to providecoverage patterns forming concentric circles combining to providesubstantially uninterrupted coverage of a predefined area around hub101. Of course, only individual antenna elements may be adjusted to havea down tilt or radiation pattern different than other antenna elementsof the tier or hub. Either arrangement could be utilized to providesubstantially homogenous communication coverage where, for example,geographic elements exist which interfere with the various radiationpatterns. Likewise, this alternative embodiment may be utilized tocompensate for any number of near/far related communication anomalies.

It can be seen in FIG. 2C that hub 101 includes outdoor unit (ODU)controller 230 coupled to each individual antenna element 200. ODUcontroller 230 is coupled to RF modem 240 and indoor unit (IDU)controller 250. Although a separate connection from ODU controller 230is illustrated to modem 240 and CPU 260, it shall be appreciated thatcommunication between ODU controller 230 and IDU controller 250 may beaccomplished through the path connecting modem 240 to the ODU controllerand CPU 260. Similarly, control information relevant to the operation ofODU controller 230 may be generated by modem 240 rather than CPU 260 andtherefore be communicated through a connection between ODU controller230 and modem 240.

ODU controller 230 includes circuitry suitable for enabling the variousantenna elements of hub 101 to communicate with RF modem 240 at theproper interval so as to transmit or receive the desired signal. In oneembodiment, ODU controller 230 includes a time division digitallycontrolled switch operating in synchronization with burst periodsdefined by IDU controller 250. Preferably, IDU controller 250 provides astrobe pulse to the switch of ODU controller 230 to provide switching insynchronization with burst periods defined by IDU controller 250. Itshall be appreciated that utilization of such a switch provides simpleintegration into the antenna array at a low cost. However, any switchingmeans synchronizable to the burst periods defined by IDU controller 250may be used if desired.

Operation of ODU controller 230 results in each individual antennaelement being in communication with IDU controller 250 according to apredetermined regimen of communication sequence timing, i.e., frames ofburst periods. This, in turn, results in each individual antenna elementbeing in communication with modem 240 within IDU controller 250. Itshall be appreciated that such switching results in the time divisionmultiplexing (TDM) of each antenna element to modem 240.

Of course, where the individual antenna elements provide bi-directionalcommunication, a second connection between ODU controller 230 and thevarious antenna elements, such as shown in FIG. 8, may be provided. Sucha connection may be utilized to provide synchronization, such as throughthe above discussed strobe pulse, to circuitry within the antennaelements to select between transmit or receive circuits at a properframe and/or burst period. Through the selection of transmit and receivecircuitry in combination with the switching of ODU controller 230, theantenna elements may be coupled to modem 240 at the proper instances toprovide bi-directional communication through modem 240 resulting in timedivision duplexing (TDD) as described in detail hereinafter with respectto a best mode of practicing the invention.

Moreover, in addition, or in the alternative, to control for TDDswitching of antenna elements, a connection between the antenna elementsand ODU 230 may be utilized for other control functions. For example, acontrol signal through such a connection may be used to dynamicallyadjust an antenna element for a particular frequency determined to besuitable for communication with a communication device during aparticular burst period of a frame. In a preferred embodiment, a controlsignal is provided by CPU 810 to a tuner, such as up/down-converters 892and 893 within antenna module 220, as shown in FIG. 8. Such a controlsignal may be provided by the control processor to program phase lockloop circuitry, or synthesizer hardware, within the various antennamodules to select a particular frequency for transmission and/orreception of communicated information. Likewise, a control signal may beprovided to adjust the amplitude of a transmitted or received signal.For example, tuners 892 and/or 893 may include amplification/attenuationcircuitry adjustable under control of such a control signal. It shall beappreciated that both of the above described control functions result ina method by which the various antenna elements may be dynamicallyconfigured to communicate with nodes of the system.

IDU controller 250 includes a processor identified as CPU 260,electronic memory identified as RAM 270, and an interface and/or routeridentified as interface/router 280. Stored within RAM 270 is a switchinginstruction algorithm to provide switching instruction orsynchronization to ODU controller 230. Buffering for informationcommunicated through modem 240 or interface/router 280 may also beprovided by RAM 270. Likewise, RAM 270 may also contain additionalstored information such as, for example, antenna element correlationtables, link management information, initialization instructions, modemconfiguration instructions, power control instructions, error correctionalgorithms, and other operation instructions discussed further below.

Although a single modem is depicted in FIG. 2C, it shall be appreciatedthat the hub system of the present invention is fully scalable toinclude any number of modems depending on the information communicationcapacity desired at the hub. Attention is directed toward FIG. 7 wherethe IDU controller of the present invention adapted for TDDcommunication is illustrated as including two modems.

Modems 240 and 700 of FIG. 7 are similarly configured to include burstmode controllers 720 and 721, QAM modulators 730 and 731, QAMdemodulators 710 and 711, as well as channel direction controlcircuitry, shown as TDD switches 740 and 741. However, it shall beappreciated that burst mode controller 721 is synchronized with masterburst mode controller 720 as well as sync channel modulator 760. Thissynchronization of burst mode controllers, illustrated as a controlsignal provided by master burst mode controller 720, is to provide ameans by which the burst periods, and thus the communication frames, ofthe modems as well as the TDMA switching of the individual antennaelements may be fully synchronized. In the preferred embodiment, thesynchronization clock is sourced from interface/router 280 and isderived from the bit stream by master burst mode controller 720. Ofcourse, synchronization may be accomplished by means other than the useof a control signal provided by a master burst mode controller, such asthe use of internal or external clock sources, if desired. One advantageof synchronization of the various components of the hub is restrictingtransmission and reception by each of the individual antenna elements topredefined time periods which allows for a greater reuse of channels asis discussed in detail with respect to the best mode for carrying outthe present invention.

It shall be understood that sync channel modulator 760 provides a meansby which the timing information of the burst mode controllers may bemodulated for provision to ODU controller 230. It shall be appreciatedthat in the preferred embodiment where CPU 260 provides control signalsto the ODU for the above discussed control functions, sync channelmodulator 760 may also include MUX 761 to provide a multiplexed signalto modulator 762.

Preferably the signals of the various modems of the hub are imposed upondifferent carrier frequencies, such as is illustrated by IF₁ of modem240 and IF₂ of modem 700. Similarly, sync channel modulator 760 imposesthe control signal including the burst mode timing information andcontrol functions on a suitable IF. These separate signals may then beeasily combined by splitter/combiner 750 for transmission through aunitary coupling to ODU controller 230. Of course the same IF could beused as a carrier by the modems of the hub if, for example, multipleconnections or a multiplexer connection were maintained between IDUcontroller 250 and ODU controller 230.

It shall be appreciated that increasing capacity by adding multiplemodems to IDU controller 250 requires circuitry in ODU controller 230 inaddition to the switch enabling TDMA access to a single data stream ofone modem discussed above. Attention is now directed toward FIG. 8wherein ODU controller circuitry corresponding to the inclusion ofmultiple modems within IDU controller 250 is shown.

It shall be appreciated that switches 870 and 871 and signalsplitter/combiners 880, 881, and 882 in combination with synchronizer830 accomplish TDMA switching of the antenna elements with respect tothe individual modems as described previously with reference to the useof a single modem. There is also illustrated, in communication with CPU810, sync channel modulator 860 utilized to demodulate the burst modecontrol signal and various other control signals provided the ODU by theunitary connection illustrated. In the preferred embodiment, wherecontrol signals are transmitted from the IDU controller to the ODUcontroller, sync channel modulator includes MUX 861 in combination withdemodulator 862 to provide CPU 810 with control information was well asproviding synchronizer 830 with timing information. Of course, wheremultiple connections are used between the ODU and IDU, sync channelmodulator 860 may be omitted.

Switches 870 and 871 are adapted to provide selection of the differentdata streams provided by each modem, as tuned to a common intermediatefrequency by tuners 840 and 841, to the antenna elements. In thepreferred embodiment, as discussed above, module 220 of the antennaelement is adapted to accept intermediate frequencies and convert themfor transmission at the desired frequency through horn 210. In thepreferred embodiment, module 220 is adapted to accept a single IF.Therefore, ODU controller 230 includes tuners 840 and 841 to adjust thevarious intermediate frequencies of the different modems, here IF₁ andIF₂, to a common intermediate frequency IF_(a). It shall be appreciated,although a single bi-directional tuner for each IF is illustrated, thata separate tuner for the transmit and receive signal path, coupled tothe bi-directional signal path by TDD switches, may be utilized ifdesired. Such an arrangement is discussed in detail below with respectto antenna module 220.

Although being adjusted to a common frequency, the signals from themodems are physically separated for switchable connection to a properantenna element, through signal combiners 880, 881, and 882, by switches870 and 871 under control of synchronizer 830. It shall be appreciatedthat, by controlling switches 870 and 871, any sequence of burst periodsfrom any modem may be transmitted by any antenna element.

Although selection of the signal modulated by a particular modem hasbeen discussed with reference to switches operating under control of asynchronizer circuit, it shall be appreciated that this function may beaccomplished by any number of means. For example, module 220 may beadapted to accept various intermediate frequencies. A variable tuner inmodule 220, such as through the use of programmable phase lock loopcircuitry, could be utilized to select a signal modulated by aparticular modem from a composite signal by tuning to a particularintermediate frequency under control of CPU 810 and synchronizercircuitry 830. Of course, where tuners are utilized to discriminatebetween the various signals modulated by the modems, tuners 840 and 841as well as switches 870 and 871 and signal combiners 880, 881, and 882may be eliminated, if desired.

It shall be appreciated that the use of short burst periods, such as onthe order of micro-seconds, requires that such a variable tuner tune toa desired frequency and reach a steady state quickly in order to avoidsignificant signal distortion. Consistent with this, experimentation hasrevealed that the use of the above mentioned switching matrix isadvantageous in providing selection of the various signals within theburst periods contemplated.

In the preferred embodiment, each antenna element is adapted forbi-directional communication. Therefore, each antenna module 220 mayinclude TDD switches 890 and 891 coupled to synchronizer 830 to providesynchronous switching the antenna element during transmit and receiveframes, as is illustrated with respect to antenna element 200.

Moreover, as it is anticipated that the communicated RF frequency of thesystem will be different than that of the IF utilized within the variouscomponents of the communication system, each antenna module 220 may alsoinclude a tuner to up-convert and/or down-convert the IF to the desiredRF for radio communication. The use of tuners to both up-convert anddown-convert the signal is illustrated in FIG. 8 as up converter 892 anddown converter 893. It shall be appreciated, although a converter isillustrated for both the transmit and receive signal path within antennamodule 220, that a single bi-directional converter may be utilized ifdesired. Of course, where a bi-directional converter is used, TDDswitches 890 and 891 may be eliminated to result in a configuration asdiscussed above with respect to IF tuners 840 and 841.

It shall be appreciated that the use of a series of converters may beutilized to accomplish the up-conversion and/or down-conversion of thesignal. For example, in the preferred embodiment where an intermediatefrequency of 400-500 MHZ and a radio frequency of approximately 38 GHzare used, a single stage converter to up-convert or down-convert betweenthe frequencies requires significant signal filtering to discriminatebetween various sidebands generated very near the frequency of interest.As such, it is preferable to up-convert and/or down-convert the signalin stages, such as through an intermediate frequency of 3 GHz.Therefore, in the preferred embodiment, converters 892 and 893 includemultiple stages of converters to up-convert or down-convert the signalbetween 400-500 MHZ, 3 GHz, and 38 GHz.

It shall be understood that an intermediate frequency closer to theradio frequency may be utilized, thus eliminating the need for bothprecise filtering of the converted signal and the above describedmulti-stage conversion. However, it shall be appreciated that it istypically more economical to manufacture a switching matrix suitable forlower frequencies than for higher frequencies. Therefore, in thepreferred embodiment, an intermediate frequency significantly lower thanthe radio frequency to be transmitted is utilized.

In the preferred embodiment, where EHF radio frequency is used, datacommunication is provided by breaking the available spectrum down intodiscrete channels for frequency division multiplexing (FDM). In the casewhere, for example 38 GHz is used, the available spectrum may be the 1.4GHz spectrum between 38.6 GHz to 40.0 GHz. This 1.4 GHz spectrum mayadvantageously be subdivided into 14 channels of 100 MHZ each. Ofcourse, as is discussed hereinafter with respect to a best mode forcarrying out the present invention, other divisions of the availablespectrum which provide a signal bandwidth sufficient to communicate thedesired information may be adopted.

To enable full duplexing using FDD as discussed above, a single 100 MHZchannel may be further subdivided into a pair of 50 MHZ channels wherebythere is defined a 50 MHZ transmit (Tx) channel and a 50 MHZ receive(Rx) channel. Of course, each 100 MHZ channel may be fully utilized aseither a Tx or Rx channel, if desired. It shall be appreciated by one ofskill in the art that utilization of the full 100 MHZ spectrum of achannel results in a half duplex channel, as no spectrum remains withinthat channel to enable reverse transmission of information. However, asis discussed hereinafter with respect to the best mode, full duplexingmay be synthesized on any single channel through the use of TDD toprovide a Tx and Rx frame within the channel.

Each Tx and Rx channel may similarly be divided into 5 discretesub-channels of 10 MHZ each, resulting in frequency-divisionmultiplexing of the 50 MHZ Tx and Rx channels. Due to the aforementionedTDMA of each antenna element, each channel is divided into predefinedTDMA time slots. These TDMA time slots may be further broken down intoprotocol time slots; a protocol time slot being a sufficient time forcommunicating an information packet formatted to a predefined protocol.For example, each 10 MHZ sub-channel may be utilized to communicatethree 10 Mbps Ethernet data packets in a 250 μsec TDMA time slotutilizing 64 QAM. Alternatively, these sub-channels may be utilized toprovide different data throughput such as one 10 Mbps Ethernet data packin a 250 μsec frame with quaternary phase-shift keying (QPSK) forexample. Furthermore, each Tx and Rx channel may be utilized as a singlechannel spanning the fill 50 MHZ bandwidth, without frequency division,if desired.

An example of sub-channel 30 Mbps communication per TDMA time slotformatted as three Ethernet data packets is shown in FIG. 3A. There the250 μsec frame contains control header 300 followed by guard time syncfield 301. Sync field 301 is followed by 10 Mbps LAN data packet 302 andforward error correction data 303, which is itself followed by guardtime sync field 304. Sync field 304 is similarly followed by 10 Mbps LANdata packet 305 and forward error correction data 306 as well as guardtime sync field 307. Sync field 307 is trailed by 10 Mbps LAN datapacket 308 and forward error correction data 309 also followed by guardtime sync field 310. It shall be appreciated that this example of 30Mbps communication is but one embodiment of the composition of a signalwithin a single channel of the present invention. There are innumerablemethods by which to utilize the above disclosed frequency spectrum forcommunication. It shall be understood that any such method may beutilized according to the present invention.

In addition to communication of information between processor-basedsystems through hub 101, control functions may also be communicatedbetween hub 101 and node 150. An example of such control communicationsis illustrated in FIG. 3A as control header 300. Alternatively, controlfunctions may be communicated through a predetermined channel orsub-channel of the FDM spectrum. These control functions might includerequests for re-transmission of a data packet, requests to adjust theamplitude of the transmitted signal, TDM timing information,instructions to adjust the modulation density, or dynamic assignment ofhub resources. The use of such control functions are discussed infurther detail below.

Information communicated to IDU controller 250 via the antenna elementsmay be re-directed by hub 101 through a backbone, such as backbone 160illustrated in FIG. 6, ultimately to other processor-based systems. Itshall be understood that a plurality of such backbone communicationsmeans may be coupled to a single hub 101.

Alternatively, information communicated to IDU controller 250 may beredirected by hub 101 through a preselected antenna element, whenswitched in communication with controller 250, ultimately to be receivedby another processor-based system. Directing attention again to FIG. 6,this communication path is illustrated, for example, by network 110communicating through hub 101 to network 120.

Larger geographical distances between two communicating processor-basedsystems may be bridged by utilization of multiple hubs. For example, asillustrated in FIG. 6, hubs 101 and 630 are in communication through anair link via antenna elements. These two hubs may provide informationcommunication between any combination of processor-based systems incommunication with either hub.

It shall be appreciated that information received by IDU controller 250of hub 101 may be re-directed in a variety of ways. In one embodiment,IDU controller 250 correlates communication through a particular antennaelement 200, or burst period associated therewith, as indicated bycontrol of ODU controller 230, with a predefined communication path.According to this method, communication received by IDU controller 250at antenna element 200 a illustrated in FIG. 2C, for example, may berouted by IDU controller 250 through antenna element 200 b, as indicatedby a correlation table, or the like, in RAM 270. Such a correlationtable, or other correlation information, could be utilized by IDUcontroller 250 to direct any communication received through a particularelement, burst period, or channel of hub 101, including a backbone, toanother particular element, burst period, or channel of hub 101. Such anembodiment is efficient where, for example, a processor-based system, incommunication with hub 101 through antenna element 200 a, is onlydesirous of communicating with a processor-based system, incommunication with hub 101 through element 200 b.

However, where a processor-based system is desirous of communicatingthrough hub 101 with a plurality of different processor-based systems,or a single antenna element is utilized by a plurality ofprocessor-based systems, the above described correlation table may beineffective. Therefore, in a preferred embodiment, informationcommunicated through hub 101 includes routing information. Suchinformation is preferably in the form of data packets conforming to theopen systems interconnection (OSI) model. An example of OSI routinginformation that may be utilized in this embodiment is the transmissioncontrol protocol (TCP) standard. However, it shall be understood thatany routing information which indicates the destination of a receiveddata packet, regardless of conforming to the OSI model, may be utilizedby the present invention if desired.

It shall be understood that modem 240 modulates and demodulatescommunication between the antenna elements and IDU controller 250.Therefore, RF communication received at any antenna element may bestored within RAM 270 as digital information. Interface/router 280 mayutilize predetermined pieces of information contained within the digitalinformation, such as may be stored in RAM 270, to determine the routingof the received communication. In the preferred embodiment, routinginformation is provided by the network layer of a data packet conformingto the OSI model. Such information would be, for example, containedwithin each LAN data packet illustrated in FIG. 3.

Upon determination of proper routing by utilizing information containedwithin the communicated information, the digital information may bere-directed by hub 101 through backbone 160 or through an antennaelement via modem 240. It shall be understood that, because of theutilization of TDMA, the digital information may be stored in RAM 270until such time as ODU controller 230 couples the correct antennaelement, as determined by the routing information, to IDU controller250, and thus provides the necessary route for communication.

Having described in detail hub 101 of the present invention, attentionis now directed toward FIG. 4 wherein node 150 is more fullyillustrated. In a preferred embodiment node 150 is comprised of twoprimary components, outdoor unit 410 and indoor unit 450, as depicted inFIG. 4.

Outdoor unit 410 includes antenna 420, module 430 and modem 440. WhereEHF is used, antenna 420 is preferably a parabolic dish antennaproviding approximately 42 dB of gain with a communication lobe ofapproximately 2 degrees. Module 430, like module 220 discussed above, isa synthesized mmWave front-end module accepting and transmitting 38 GHzRF through antenna 420 converted to an IF in the range of 400-500 MHZfor communication with RF modem 440. Preferably, module 430 includes thevarious tuner and TDD switching components illustrated in FIG. 8 withrespect to module 220. However, it shall be understood that any numberof component configurations are acceptable for use in module 430, asthey are in module 220. It shall be appreciated that the linkillustrated between CPU 460 and module 430 may provide a signalcontrolling the synchronized switching the synchronized switching of theTDD switches according to a TDD frame of an associated hub. Modem 440may be a variable rate modem, having a fixed baud rate with a variabledensity of bits per symbol, corresponding to the use of a variable ratemodem utilized at an associated hub. Of course the antenna and moduleattributes of node 150 may be different than that stated above where,for example, a different carrier frequency or beam pattern is desired.

Indoor unit 450 includes CPU 460, RAM 470 and interface 480. It shall beunderstood that indoor unit 450 and outdoor unit 410 are coupled suchthat information received by antenna 420 as RF energy is communicated toindoor unit 450.

Interface 480 provides data communication between indoor unit 450, andthus node 150, and a processor-based system such as LAN 490 illustratedin FIG. 4. Furthermore, interface 480 formats the data communication tobe compatible with the processor-based system so coupled. As forexample, where LAN 490 is coupled to node 150, interface 480 may bothsend and receive Ethernet data packets where LAN 490 utilizes Ethernetcompatible communication protocol. However, where node 150 is coupled toa single computer, it may be advantageous for interface 480 to provideasynchronous receive/transmit protocol. It shall be appreciated by oneof skill in the art that interface 480 may include multiplecommunications protocols within a single embodiment, being userselectable, or may be individual modules to be included withincontroller 450 as needed.

RAM 470 is coupled to both interface 480 and CPU 460. Where TDM is beingused at hub 101, RAM 470 may store information received at node 150through interface 480 while awaiting transmission to hub 101. RAM 470may also contain additional stored information such as, for example,initialization instructions and link management information such asmodem configuration instructions, power control instructions and errorcorrection instructions discussed in detail below.

Having described hub 101 and node 150 of the present invention indetail, interaction of these elements shall now be described. Asdiscussed above, RAM 270 of hub 101 and RAM 470 of node 150 may includeinstructions for the operation of CPUs 260 and 460 respectively. Theseinstructions may include, for example, a method for programming hub 101and node 150 for communication and a method for link managementincluding communication error correction.

Additionally, both RAM 270 and RAM 470 may temporarily store informationcommunicated via the device for re-transmission in the case atransmission error is detected. Transmission error may be detected byCPUs 260 and 460 by various methods. One such method well known in theart is the transmission of error detection information accompanyingtransmitted data packets. Such a method is defined in the data linklayer of the aforementioned OSI model.

Attention is directed toward FIGS. 3A and 3B, wherein each of the threeillustrated data packets includes associated forward error correction(FEC) information. It shall be appreciated that FEC information mayinclude a summary indication of the content of the associated datapacket by such means as a checksum, a parity indication, or the like.This summary indication may be generated by the transmitting CPU, CPUs260 or 460, or may be integral to the particular transmission protocolutilized by the processor based systems as, for example, data packetsconforming to Ethernet protocol. Regardless of its source, thisinformation may be utilized to detect errors in the transmitted data andto subsequently correct the error such as by requesting retransmissionof the effected data packets.

As discussed above, both RAM 270 and RAM 470 store communicatedinformation in a form readable by CPUs 260 and 460 respectively.Therefore, CPUs 260 and 460 may utilize predetermined pieces ofinformation contained within the digital information in RAM 270 and RAM470 respectively to detect communication errors. For example in theembodiment illustrated in FIG. 3A, the receiving CPU may generate asummary indication of the content of each LAN data packet stored withinRAM and compare this to the associated FEC information. Upon determininga difference between the two summary indications, the receiving CPU mayrequest re-transmission of the LAN data packet by the sending CPU.

However, in a preferred embodiment, the FEC information includes dataredundancy in the data stream using special encoders. Upon detection ofa transmission error, decoders available at a recipient site may beutilized to provide error correction of portions of the data stream.Such error correction from encoded redundant data is capable ofcorrecting transmitted information which includes up to a predeterminedpercentage of errors in the transmission. Preferably, the FECinformation so utilized is a block code such as the Reed-Solomon FECprotocol.

For example in the embodiment illustrated in FIG. 3B, the receiving CPUmay decode information transmitted within the FEC data packet andcompare this information to the content of each ATM data packet storedwithin RAM. Upon detecting a transmission error through such comparison,the receiving CPU may correct the ATM data packet utilizing redundantdata encoded in the FEC data packet. Of course, where transmission ofthe data packet is effected to the point of being beyond correctionutilizing the encoded redundant data of the FEC data packet,retransmission of the data packet may be utilized, if desired.

As previously discussed, a predetermined sub-band of a communicationchannel may be utilized for the transmission of control functions suchas the above mentioned re-transmission request or other controlfunctions, such as power level adjustment and information densityadjustment. Alternatively, control functions may be included in eachTDMA burst transmission as, for example, control header 300 illustratedin FIG. 3A or control channel block 363 illustrated in FIG. 3B. Forexample, the corresponding CPU will detect the request forre-transmission present in the predetermined control function sub-bandor control header and respond with re-transmission of the requested LANdata packet.

Of course, if error free transmission of information or if errorcorrection of the transmitted information is handled by another means,the above method of error correction may be omitted if desired.Furthermore, if TDM is not utilized and error correction byre-transmission of information is not desired, storage of communicationinformation in RAM 270 and RAM 470 may also be omitted.

The preferred embodiment also includes a link maintenance algorithm tomonitor communication parameters, such as errors in communications,associated with particular nodes 150 in RAM 270 of the hub. Upondetermination of the existence of unacceptable communication parameters,such as an unacceptable error rate as determined by comparison to apredetermined acceptable error rate, CPU 260 may transmit an instructionto the particular node to make appropriate adjustment. For example, CPU260 may instruct node 150 to adjust communication transmission power toachieve an acceptable error rate or to adjust the M-ary QAM signalinglevel (i.e., adjust the number of bits per symbol, hereinafter referredto as the QAM rate) at which information is transmitted. Of course, CPU260 may also provide such control signals to the various QAM modulatorsassociated with the hub to result in the proper modulation/demodulationof the signal communicated to the node. As above, these controlfunctions associated with link maintenance may be communicated betweenCPU 260 and CPU 460 by means of a designated control function sub-bandor control header.

Upon detecting a control instruction to adjust communications, CPU 460provides the necessary instruction to the proper component. For example,as discussed above with respect to the hub, CPU 460 may cause module 430to adjust transmission power or may cause modem 440 to adjust the QAMrate, depending on the attribute effected or the control informationtransmitted by the hub.

For example, a control signal may be provided by CPU 460 to a tunerwithin antenna module 430. Such a control signal may be provided by thecontrol processor to program phase lock loop circuitry, or synthesizerhardware, within the antenna module to select a particular frequency fortransmission and/or reception of communicated information. Likewise, acontrol signal may be provided to adjust the amplitude of a transmittedor received signal. For example, tuners within module 430, such as thoseillustrated in module 220 in FIG. 8, may includeamplification/attenuation circuitry adjustable under control of such acontrol signal. These attributes, as well as the adjustment of theinformation density of communicated data, may be made by the node inresponse to a determination node at the hub and communicated through acontrol channel or may be made by an algorithm at the node. It shall beappreciated that adjustment of some attributes by the node may require acorresponding adjustment at the hub, such as with adjustment of QAM rateor channel. Therefore, the node may communicate control functions to thehub in such situations.

It shall be appreciated that periodic adjustment of communicationparameters may be necessary, even where an initialization algorithm, asdiscussed in detail below, has been utilized to properly initialize suchcommunication parameters, because of the occurrence of anomalieseffecting communication. For example, although an initial QAM rateand/or transmission power level may be selected upon initialization ofcommunication, various atmospheric conditions, such as rain, may causesignificant signal attenuation. Therefore, it is advantageous to monitorcommunication parameters to provide adjustment compensating for theoccurrence of such anomalies. It shall be appreciated that themonitoring of communication parameters and communication of controlfunctions may be from a node to a hub where such node has detectedunacceptable communication attributes.

In addition to storing communication information and associated linkmaintenance algorithms, in the preferred embodiment RAM 470 is utilizedto store instructions to be utilized by CPU 460 in operating node 150.Such instructions may include channels in the available spectrum not tobe utilized by node 150, windows of communication available forcommunication between node 150 and hub 101 due to TDM, and synchronizinginformation, such as frame timing and propagation delay offset, toenable TDM and/or TDD communication. Furthermore, RAM 470 may also storeinstructions to be utilized by CPU 460 for dynamic assignment of hubresources such as the above mentioned channels available forcommunication and windows of communication, or burst periods, asdiscussed hereinafter.

It shall be appreciated that, although in the preferred embodiment theantenna elements of hub 101 and antenna 420 of node 150 are pre-selectedto use narrow beams, environments in which the invention is likely to beutilized may include physical topology causing reflection of transmittedsignals. Such reflections are prone to causing multi-path interferencein communication between node 150 and hub 101. Therefore, RAM 470includes an initialization algorithm as part of the above mentionedcommunication instructions. Of course, such an initialization algorithmmay be stored in a processor-based system in communication with node 150to achieve the same results if desired.

The initialization algorithm operates in conjunction with a similaralgorithm stored at hub 101. As with the initialization algorithm ofnode 150, the initialization algorithm utilized by hub 101 alternativelymay be stored in a processor-based system in communication with hub 101to achieve the same results. The initialization algorithm at hub 101operates to cause node 150 to transmit a predetermined signal over theavailable spectrum to enable the mapping of communication parameters,such as signal strength, as received at each antenna element of hub 101.This information may then be utilized by the present invention todetermine the individual antenna elements best suited for communicationbetween node 150 and hub 101. This in turn determines the timing ofcommunication windows, or burst periods, available to node 150 accordingto the TDM of these antenna elements. This timing information may thenbe stored in RAM 470 to enable CPU 460 to time transmission throughantenna 410 to achieve synchronization with the switching of antennaelements by ODU controller 230. Of course, it may not be advantageous toutilize such initialization algorithms where, for example, multi-pathand co-channel interference are not concerns. Therefore, the use of suchinitialization algorithms may be omitted, if desired.

Additionally, where a plurality of nodes are to be in communication withhub 101, co-channel interference may result from communication betweenseveral nodes. Therefore, the initialization algorithm discussed abovemay be instigated at each such node with hub 101 storing thecommunication parameters for each node. Thereafter, hub 101 maydetermine the possibility of co-channel interference between severalnodes 150 and limit communication at each such node 150 to a subset ofthe available spectrum, i.e. assign different channels or burst periodsto each such node 150. Additionally, this information may be utilized inthe dynamic assignment of hub resources for use by a particular node.Such dynamic assignment may involve the temporary assignment of channelsor burst periods previously assigned to a first node to another suchnode in times of under-utilization by the first node.

The communication parameter information for each node may be utilized todetermine the initial QAM rate, available with a variable modem asdiscussed above, to be utilized for a particular node. The initial QAMrate determination may be made based on a particular signal strengthproviding a suitable carrier to noise (C/N) ratio for a particular QAMrate. For example, a C/N ratio (BER=10⁻⁶) of 11 dB has been found to besufficient to sustain a modulation of 4 QAM. Similarly, a C/N ratio(BER=10⁻⁶) of 21.5 dB has been found to be sufficient to sustain amodulation of 64 QAM.

Of course, as signal strength attenuates with distance, the QAM ratedetermination may alternatively be made by measuring the propagationdelay of a transmitted signal, and thus the distance from the hub to thenode. In the preferred embodiment, the propagation delay, and thereforethe distance between node and hub, is determined by the node initiallysynchronizing to the frame timing established by the hub. Thereafter,the node transmits a shortened burst during a predetermined time slot.This transmitted burst will be offset from the hub frame timing by thepropagation delay time. The hub utilizes this offset to compute thepropagation delay, and thus the distance from the hub, associated withthe transmitting node. Thereafter, a particular propagation delay ordistance may be associated with selection of a particular QAM rate forthe node.

Regardless of how the determination is made, the selection of a maximumQAM rate for a particular node allows for more efficient use of theavailable spectrum by increasing information density to those nodeshaving suitable communication attributes. Such increased informationdensities are possible, for example, to nodes located near the hubwithout an increase in transmission power as compared to less denseinformation communication to nodes located far from the hub.

Attention is now directed to FIG. 5 wherein a preferred embodiment ofthe initialization algorithm of hub 101 is illustrated. Although asingle iteration of the initialization program illustrated, it shall beunderstood that the initialization program may be repeated for each nodein communication with hub 101 to create a data set reflectingcommunication attributes of each node with respect to hub 101.

At step 501 antenna element counter N is initialized. It shall beappreciated that antenna element counter N may be utilized by theinitialization program to reference the N number of individual antennaelements comprising the antenna array of hub 101. Thereafter, at step502, antenna element counter N is incremented by one.

At step 503 the initialization program transmits a control signalthrough antenna element N requesting a node to transmit a predeterminedsample signal. It shall be understood that transmission of the controlsignal is directed toward a predetermined node. The node may be selectedfrom a data set of nodes known to be in communication with hub 101, orit may be selected by operator input such as a control signal from anode, or it may be determined from responses to a polling signalbroadcast from hub 101.

At step 504 the initialization program monitors antenna element N for apredetermined period of time. It shall be understood that the amount oftime the antenna element is monitored is predetermined to be an adequateamount of time for signals from the node, sufficient to cause multi-pathinterference, to be received. In a preferred embodiment, thepredetermined amount of time for monitoring antenna element N is thetime required for one complete TDM cycle through all N antenna elementsof hub 101.

At step 505 it is determined whether a predetermined sample signal wasreceived by antenna element N within the predetermined monitoring time.If no such sample signal was received, then it is assumed antennaelement N is not in communication with the node for which initializationinformation is being sought. Therefore, the initialization programproceeds to step 509 to determine if all antenna elements have beenmonitored. If not, the program returns to step 502 and increments theantenna element indicator to monitor additional antenna elements.

It shall be understood that the transmission of a control signal andsubsequent monitoring for a sample signal may be repeated at a singleantenna element N. Repeated iterations at antenna element N may beutilized to provide a more accurate sample by statistically analyzingmultiple results, thus, disregarding or minimizing anomalous resultscaused by superseding factors.

If a sample signal is detected at antenna element N, however, theinitialization program continues to step 506 and determines thepropagation delay of transmission of a signal from the node. It shall beunderstood that by knowing the time of transmission of the controlsignal from antenna element N and the time of reception of the samplesignal at antenna element N, the initialization program can determinethe propagation delay of a signal transmitted from a node to hub 101.Additionally, to increase the accuracy of this determination, theinitialization program may analyze multiple transmissions as discussedabove.

The initialization program also determines the signal strength of thesample signal received at antenna element N at step 507. It shall beunderstood that signal strength information is useful in determiningindividual antenna elements of hub 101 most desirable for utilizationfor communication between hub 101 and the node. Moreover, as discussedabove, the signal strength and/or distance information determined by theinitialization program may be used to select a QAM rate to providemaximum possible information density communication to a particular node.It shall be appreciated that, although such QAM selection is discussedhere in reference to initializing communication parameters, such adetermination may also be made dynamically throughout subsequentcommunications between various nodes and the hub.

At step 508 the initialization program stores information determined inthe above steps in a data set associated with the particular noderesponding to the control signal. It shall be understood that suchstored information may be utilized by hub 101 not only for initiallyassigning channels and individual antenna elements for communicationwith the node, but may also be utilized to dynamically configurecommunications between the devices in the case of hardware failure orother event causing communication interruptions.

At step 509 the initialization program determines if all N antennaelements have been accessed by the above steps. If not, theinitialization program returns to step 502 to increment antenna elementcounter N. If all antenna elements have been accessed the initializationprogram ceases operation with respect to the selected node.

Having stored, in a data set associated with the node, attributesassociated with communication through each antenna element of hub 101,the initialization program may then perform statistical analysis on thedata to determine communication parameters such as a primary andsecondary antenna element through which communications between a selectnode and hub 101 may take place. It shall be appreciated thatinformation contained in the data set such as a high signal strength anda short propagation delay detected at an antenna element indicates theprobability of a direct air link between the node and hub 101. As suchthe initialization program may assign this antenna element forcommunication with the selected node. Because each antenna element is inTDM communication with the RF modem, this assignment also identifies thetiming of communication windows between the node and hub 101.

As discussed above, the mapping of communication characteristics may berepeated for each node. Therefore, the above statistical analysis mayalso compare communication attributes of other nodes when assigningantenna elements for communication with a selected node. For example, ifone antenna element is determined to provide optimum communicationbetween hub 101 and more than one node, only select channels availablein the spectrum may be assigned to each such node. Or, as discussedhereinafter with respect to a best mode for carrying out the presentinvention, each such node may be assigned different TDM bursts within achannel within which to accomplish communication. Alternatively, theinitialization program may assign such an antenna element to only onesuch node and assign a secondary antenna element, possibly providingless than optimum communication, to another such node.

Upon determining the assignment of antenna elements and channels forones of the nodes in communication with hub 101, the initializationprogram transmits control signals to these nodes. The control signal mayinclude information regarding the channels available for communicationbetween a specific node as well as timing information to allowsynchronization of communication between the node and the TDM antennaelement of hub 101.

The timing information provided by the hub may include theaforementioned offset, determined during link initialization, to allow anode to anticipate transmission of a burst period to the hub, or retardreception of a burst period from the hub, by a time period sufficient toadjust for the signal propagation delay. It shall be appreciated thatinclusion of such offset information in the TDM timing informationallows for maximum information communication during a burst period. Ofcourse, where maximum information communication is not desired, thetiming information may not include any offset information. Here, a delayperiod, in which no information is transmitted, of sufficient durationto accommodate the propagation delay may be included in the burstperiod. However, it shall be understood that such a method ofcompensating for the signal propagation delay trades a decrease ininformation throughput in order to accommodate the delay.

As discussed previously, control information may be communicated by thehub through a predetermined sub-channel utilized for control informationor may be included within a logical channel or control channel embeddedin the communication data packet as discussed above. A node receivingsuch control information will store it in RAM 470 for later utilizationby CPU 460. Of course, where FDD is utilized by hub 101, it isunnecessary for RAM 470 to include timing information regardingcommunication windows with hub 101 and, therefore, such information maybe omitted from the control information. Likewise, where communicationbetween the hub and node is accomplished only upon a single channel,information regarding channels available for communication may beomitted from this control information.

As discussed above, this initialization information may also be utilizedby the hub for dynamic allocation of hub resources to the nodes incommunication therewith. It shall be understood that by monitoringinformation communication between the nodes and the hub on a continuingbasis, the hub may determine utilization statistics of any particularnode. If it is determined that any such node is under-utilizing hubresources available to the node, such as, for example, not transmittinginformation over a channel allotted to the node, the hub may reassignsuch resources, or portion thereof, to another node. It shall beappreciated that this reassignment may be accomplished by the use of thecontrol signals discussed in detail above.

Having described various embodiments of the operation of the presentinvention in detail, a contemplated best mode for practicing thisinvention will now be described. The foregoing discussion has describedboth frequency division duplexing (FDD) and time division duplexing(TDD) as means by which to enable a full duplex link between the hub anda node or subscriber. The best mode for practicing this invention iscontemplated to be by using a TDD arrangement is described herebelow.This best mode will be described with respect to FIGS. 7 and 8.

Experimentation has revealed that the utilization of a single channel ateach antenna element of hub 101 providing TDD Tx and Rx frames, such asframes 351 and 352 illustrated in FIG. 3B, allows a desirable reusefactor of available channels. It shall be understood that a cellularfrequency reuse pattern of a plurality of hubs of the present inventionis envisioned. Such a cellular pattern presents added complexity in thereuse of individual channels as the use of the channels at each hub mustalso take into consideration use of channels at adjacent hubs.

To minimize the potential for co-channel interference and, to a certainextent, multi-path interference, synchronization of transmission andreception at each antenna element is desirable. For example each antennaelement of hub 101 will transmit only during a predetermined Tx frameand will receive only during a predetermined Rx frame. Likewise, eachhub of a network of such hubs may be synchronized to transmit andreceive only during the same predetermined Tx and Rx frames. It shall beappreciated that the above scheme defines a TDD communication system.

Dividing the available spectrum into discrete channels of 10 MHZ eachprovides a convenient means by which to practice the present invention.Preferably, each antenna element of hub 101 is adapted to transmit andreceive at least a single 10 MHZ channel as defined by the system. Asdescribed above, antenna elements adapted for a particular 10 MHZchannel may be distributed throughout hub 101 to provide for reuse ofeach defined channel.

Additionally, each Tx and Rx frame may be divided into discrete burstperiods to provide for TDMA utilization of each channel. Preferably Txand Rx frames, each being 250 μsec, are divided into eight burstperiods, as is illustrated in FIG. 3B, whereby full duplexing may besynthesized in sixteen such burst periods. As previously described, theTDMA burst periods may be further broken down into protocol time slots;a protocol time slot being a sufficient time for communicating aninformation packet formatted to a predefined protocol. For example, eachchannel may be utilized to communicate two 53 byte ATM cells in a TDMAburst period utilizing QAM.

It shall be appreciated that the use of 53 byte ATM cells is preferredas the protocol includes an 5 byte header that may be utilized by thepresent invention for routing information, as is discussed in detailhereinbefore. Additionally, the use of 53 byte ATM cells provides asufficiently compact data packet to provide acceptable latency periodswhen transmitting full duplex voice or other signals sensitive to delayor signal latency.

A preferred embodiment of information formatting within a TDMA burstperiod is illustrated as burst 360 in FIG. 3B. Here each burst containsramp 361 followed by preamble 362. Preamble 362 is followed by CCH block363. CCH block 363 is followed by ATM cells 364 and 365 which in turnare followed by FEC block 366. FEC block 366 is similarly followed byramp 367.

It shall be understood that in the above identified TDMA burst periodramps 361 and 367 are time segments within the burst period to allow fora transmitter to come to full power and to again de-energize withoutaffecting the power at which message information is transmitted.Preamble 362 and forward error correction (FEC) block 366, like the rampcomponents, are system overhead components and are used to aid in thetransmission of information contained in ATM cells 364 and 365.Specifically, preamble 362 contains a dotting pattern to resynchronizethe symbol clock at a receiving site. FEC 366 provides for errordetection and correction of the transmitted information. Control channel(CCH) 363, as previously discussed, is provided to communicate systemcontrol information.

It shall be appreciated that this example of information formatting isbut one embodiment of communication utilizing TDMA burst periods. Thereare innumerable methods by which to utilize the above disclosed burstperiods of the Tx and Rx frames for communication. For example, any ofthe above components could be deleted, as well as any number ofdifferent components added, if desired. Therefore, it shall beunderstood that the present invention is not limited to the format ofthe TDMA burst period illustrated.

It shall be appreciated that through the use of QAM as previouslydiscussed, the information density of each ATM cell of burst 360 may beincreased. For example, using two ATM cells, as illustrated in FIG. 3B,with 4 QAM, the time slot capacity realized is ½ DS1. Moreover, byutilizing increased modulation, this capacity may be increased. Using 16QAM the time slot capacity realized is 1 DS1; using 64 QAM the time slotcapacity realized is 1½ DS1; and using 256 QAM the time slot capacityrealized is 2 DS1. It shall be understood that any combination of thesedensities may be realized by a single hub and/or antenna element byusing the variable rate modem and initialization algorithm discussedpreviously.

It shall be understood that the burst periods of each Tx and Rx framemay be utilized by a single antenna element to provide channel TDMA tomultiple nodes located within the antenna element's radiation pattern.For example, burst periods 1 and 2 may be used by an antenna element toprovide communication to a first node while burst periods 3 through 7are used by the same antenna element to provide communication to asecond node. Likewise, a single Tx or Rx frame may be utilized bydifferent antenna elements. For example, burst periods 1 through 4 maybe used by a first antenna element to provide communication to a firstnode while burst periods 5 through 8 are used by a second antennaelement to provide communication to a second node.

It shall be appreciated that combinations of the above mentioned TDMAuse of the burst periods by a single antenna element and division of Txand Rx frames between different antenna elements may be utilized by thepresent invention. For example, burst periods 1 and 2 may be used by anantenna element to provide TDMA communication to a first node and secondnode while burst periods 3 and 4 are used by a second antenna element toprovide communication to a third node.

Although balanced duplexing is illustrated by the eight forward channeland eight reverse channel burst periods in FIG. 3B, it shall beunderstood that any combination of forward and reverse channeldistribution may be utilized by the present invention. Of course, whereall burst periods are utilized in either the forward or the reversedirection, time division duplexing is no longer accomplished by thatchannel.

Experimentation has revealed that information communicated by a systemsuch as that of the present invention generally falls into one of threecategories; those being substantially balanced full duplexcommunication, principally downlink communication, and principallyuplink communication. Therefore, these communication needs may besatisfactorily met by one embodiment of the present invention byutilizing any one of three duplexing schemes for a particularsubscriber.

The first duplexing scheme is the 50% forward/50% reverse channeldistribution of burst periods described above with reference to TDD. Itshall be appreciated that the 50%/50% distribution is advantageous wherea significant amount of information is both being communicated downlinkas well as uplink.

The second duplexing scheme is where approximately 94% of the burstperiods are utilized to transmit information from the hub to a node(downlink), and the remaining 6% of the burst periods are utilized totransmit information in the reverse direction (uplink). Preferably sucha 94%/6% duplex scheme is realized by utilizing fifteen of the sixteenburst periods illustrated in FIG. 3B as downlink burst periods andutilizing the remaining one burst period as an uplink burst period.

The 94%/6% distribution is advantageous where a significant amount ofinformation is being communicated downlink, but little, or no,information is being communicated uplink. It shall be appreciated thatthe 6% reverse channel communication is preferably maintained by thepresent invention, even where there is no reverse channel informationcommunication desired by the subscriber, as this small amount ofbandwidth may be utilized by the system for link maintenance and controlfunctions such as those described previously. For example, this 6%reverse channel communication may be used to request re-transmission ofa data packet, requests to adjust the amplitude of the transmittedsignal, TDM timing information, dynamic assignment of hub resources, ormay be used to monitor communications attributes for the periodicadjustment of QAM modulation.

The third duplexing scheme is where approximately 6% of the burstperiods are utilized to transmit information from the hub to a node(downlink), and the remaining 94% of the burst periods are utilized totransmit information in the reverse direction (uplink). It shall beappreciated that this scheme is simply the inverse of the abovediscussed 94%/6% scheme providing for substantial informationcommunication in the uplink direction.

Although it is possible to define the TDD frames in combinations otherthan the three discussed above, as well as defining Tx and Rx framecombinations of each of these various schemes to include differentnumbers of individual burst periods, the preferred embodiment limits theschemes used to a predetermined number of combinations, each of whichinclude the same total number of burst periods. It shall be appreciatedthat the three combinations of duplexing discussed above satisfactorilyservice the generally experienced information communicationrequirements. Moreover, use of a linked number of TDD schemes, each ofwhich completing a forward and reverse channel communication frame inthe same total number of burst periods, is advantageous in the reuse ofchannels throughout the system. By limiting the number and timing ofsuch schemes, reuse patterns of the various channels in both a singlehub as well as a cellular frequency reuse pattern are simplified.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

What is claimed is:
 1. A method for information communication between aplurality of physically separated processor-based systems utilizing aplurality of communication nodes providing directional communication ina predetermined lobe directed toward a communication hub having aplurality of antenna units, said method comprising the steps of:coupling each one of said plurality of nodes to ones of said pluralityof systems; directing an antenna of each node to result in saidpredetermined lobe being operably aligned with said hub; transmittinginformation from a select one of said plurality of systems through acoupled node to a predetermined antenna unit of said plurality ofantenna units of said hub; receiving said transmitted information fromsaid select one of said plurality of systems at said hub; and routingsaid received information to at least one system of said plurality ofsystems by said hub.
 2. The method of claim 1, wherein said receivedinformation comprises a signal which is time divided to include aplurality of information bursts.
 3. The method of claim 2, wherein saidplurality of information bursts comprise a set of forward channelinformation bursts and a set of reverse channel information bursts,wherein the duration of said forward channel and reverse channelinformation bursts are adjustable with respect to each other.
 4. Themethod of claim 2, wherein said plurality of information bursts comprisea set of forward channel information bursts and a set of reverse channelinformation bursts, said forward and reverse channel information burstsdefined to comprise a percentage of said plurality of information burstsselected from the group consisting of: approximately 94% forward channelinformation bursts and approximately 6% reverse channel informationbursts; approximately 50% forward channel information bursts andapproximately 50% reverse channel information bursts; and approximately6% forward channel information bursts and approximately 94% reversechannel information bursts.
 5. The method of claim 1, wherein said stepof transmitting information from a select one of said plurality ofsystems through a coupled node comprises the substeps of: receiving saidinformation from said coupled one of said plurality of systems at saidcoupled node; storing said received information in an electronic memoryat said node; and formatting said received information into a formsuitable for transmission to said hub, said formatted informationincluding routing information indicating at least one system of saidplurality of systems to receive said information.
 6. The method of claim1, wherein said step of receiving information comprises the use of amodem adapted for variable information density modulation.
 7. The methodof claim 6, wherein said variable information density modulationincludes the use of quadrature amplitude modulation.
 8. The method ofclaim 6, wherein said step of receiving information from a select one ofsaid plurality of systems at said hub comprises the substep of storingsaid received information in an electronic memory at said hub.
 9. Themethod of claim 8, wherein said step of routing said receivedinformation to said at least one system indicated by said routinginformation comprises the substep of reading routing information from apredetermined location within said electronic memory containing saidreceived information.
 10. The method of claim 9, wherein said step ofrouting said received information to said at least one system indicatedby said routing information further comprises the substep oftransmitting said information stored in said electronic memory throughan information communication backbone coupled to said hub.
 11. Themethod of claim 9, wherein said step of routing said receivedinformation to said at least one system indicated by said routinginformation further comprises the substep of transmitting saidinformation stored in said electronic memory to a node of said pluralityof nodes, said node being coupled to said at least one system indictedby said routing information.
 12. The method of claim 1, wherein saidstep of routing said received information to said at least one systemcomprises the substep of determining a route from information storedwithin said hub.
 13. The method of claim 1, further comprising the stepof initializing said communication hub for information communicationwith ones of said plurality of nodes, said initializing step comprisingthe substeps of: determining communication attributes between said huband of each of said plurality of nodes; and assigning resourcesavailable at said hub to be utilized by each of said plurality of nodesbased at least in part on said determined communication attributes. 14.A method for information communication between a plurality of physicallyseparated processor-based systems utilizing a plurality of communicationnodes providing directional communication in a predetermined lobedirected toward a communication hub having a plurality of antenna units,said method comprising the steps of: coupling each one of said pluralityof nodes to ones of said plurality of systems; directing an antenna ofeach node to result in said predetermined lobe being operably alignedwith said hub; transmitting information from a select one of saidplurality of systems through a coupled node to a predetermined antennaunit of said plurality of antenna units of said hub; receiving saidtransmitted information from said select one of said plurality ofsystems at said hub, wherein said received information comprises asignal which is time divided among signals of other ones of saidplurality of systems received through other antenna elements of saidplurality of antenna units of said hub; and routing said receivedinformation to at least one system of said plurality of systems by saidhub.
 15. The method of claim 14, wherein said time divided signalcomprises a set of forward channel information bursts and a set ofreverse channel information bursts, wherein said forward and reversechannel information bursts are dynamically adjustable with respect toeach other.
 16. The method of claim 15, wherein dynamic adjustment ofsaid forward and reverse channel information bursts are selected tocomprise a percentage of said time divided signal selected from thegroup consisting of: approximately 94% forward channel informationbursts and approximately 6% reverse channel information bursts;approximately 50% forward channel information bursts and approximately50% reverse channel information bursts; and approximately 6% forwardchannel information bursts and approximately 94% reverse channelinformation bursts.
 17. The method of claim 14, wherein said step oftransmitting information from a select one of said plurality of systemsthrough a coupled node comprises the substeps of: receiving saidinformation from said coupled one of said plurality of systems at saidcoupled node; and formatting said received information into a formsuitable for transmission to said hub, said formatted informationincluding routing information indicating at least one system of saidplurality of systems to receive said information.
 18. The method ofclaim 14, wherein said step of receiving information comprises the useof a radio frequency modem adapted for variable information densitymodulation.
 19. The method of claim 18, wherein said variableinformation density modulation includes the use of quadrature amplitudemodulation.
 20. The method of claim 14, wherein said step of routingsaid received information to said at least one system comprises thesubstep of determining a route from information stored within said hub.21. The method of claim 14, further comprising the step of initializingsaid communication hub for information communication with ones of saidplurality of nodes, said initializing step comprising the substeps of:determining communication attributes between said hub and of each ofsaid plurality of nodes; and assigning resources available at said hubto be utilized by each of said plurality of nodes based at least in parton said determined communication attributes.
 22. A method forinformation communication between a plurality of processor-basedsystems, said method comprising the steps of: directing an antenna of aselect one of said plurality of systems to result in a predeterminedlobe being operably aligned with a predetermined interface of a hub;transmitting information from said select one of said plurality ofsystems to said predetermined interface of said hub, wherein saidpredetermined interface is one of a plurality of hub antennas; receivingsaid transmitted information from said select one of said plurality ofsystems at said hub, wherein said received information comprises asignal which is time divided to include a plurality of informationbursts including a set of forward channel information bursts and a setof reverse channel information bursts, wherein the duration of saidforward channel and reverse channel information bursts are adjustablewith respect to each other; and routing said received information to atleast one system of said plurality of systems by said hub.
 23. Themethod of claim 22, wherein said duration of said forward channel andreverse channel information bursts is selected from the group consistingof: approximately 94% forward channel information bursts andapproximately 6% reverse channel information bursts; approximately 50%forward channel information bursts and approximately 50% reverse channelinformation bursts; and approximately 6% forward channel informationbursts and approximately 94% reverse channel information bursts.
 24. Themethod of claim 22, wherein said step of receiving information comprisesthe use of a modem adapted for variable information density modulation.25. The method of claim 24, wherein said variable information densitymodulation includes the use of quadrature amplitude modulation.
 26. Themethod of claim 22, wherein said step of routing said receivedinformation comprises the substep of reading routing information from apredetermined location within an electronic memory of said hub.
 27. Themethod of claim 22, wherein said step of routing said receivedinformation comprises the substep of determining a route frominformation included in said reverse channel information bursts.
 28. Themethod of claim 22, further comprising the step of initializing saidcommunication hub for information communication with ones of saidplurality of nodes, said initializing step comprising the substeps of:determining communication attributes between said hub and of each ofsaid plurality of nodes; and assigning resources available at said hubto be utilized by each of said plurality of nodes based at least in parton said determined communication attributes.